Yeah...we got paid to do that...and I loved it.
So, to answer what’s going on in the video you see, let’s first talk about the cat shot. EMALS is the new technology, electromagnetic induction to provide the force to accelerate an airplane from dead stop to about 170 knots in a space just under 100 meters. Steam is the old, and still prevalent, technology.
The catapult (as opposed to ski jumps, or VTOL) allows the use of heavier and higher performance airplanes. It also requires less free flight deck space than a ski jump and more launch capability in a given window.
The catapults as installed on a USN carrier accelerate the airplane to flying speed by connecting a shuttle (which is a fitting connected to the motive force, steam tubes, induction motor, etc. below the deck) to the airplane. On very old airplanes like the F-4 and F-8, a cable known as a bridle was used. Current airplanes all have a launch bar, that is a steel bar, connected to the nose gear, that engages the shuttle. The launch bar is normally retracted.
When the launch bar is hooked into the shuttle, all slack has to be removed, or the shock load from the cat firing would break the bar and the airplane*. So, a second fitting is used, called a “hold back” and the holdback does just that: hold the airplane back against full engine power. This allows the shuttle to securely engage the launch bar, and the engines to be placed at full power, so that everything is ready when the cat is fired.
The catapult officer does a set of calculations based on aircraft type, weight, wind, temperature, and available steam/energy. The impulse is calculated to provide enough energy to get that airplane launched with that set of conditions. On a windy day, say, when the carrier is making 25-30 knots of wind, and when the airplane is light, say, in the case of a Tomcat at 54,000 lbs, the cat shot is sweet, about 2G acceleration (makes a Tesla in ludicrous mode look slow).
But with light wind, hot day (air density lower, so more speed is needed) and a heavy airplane, say, a 69,000# Tomcat loaded for combat, the cat shot can be brutal. Over 3G acceleration (perhaps more than 4G, as I did some math...) to achieve that flying speed in under two seconds. It's also brutal because the nose strut extends at the end of the stroke and there is a big change in the rate of acceleration (third derivative of position with respect to time, known as "jerk"). Makes for quite a jolt on a heavy shot.
The basic sequence (no arming of weapons) -
The airplane is guided into the catapult by the yellow shirt (taxi director). Yep, they’re so good that the airplane is within the 1/2” needed to be aligned with the shuttle. The airplane unfolds/spreads wings and the blast deflector is raised (a big shield behind the airplane to protect everyone/thing from the jet exhaust). The launch bar is lowered and the airplane taxied into the shuttle. The holdback is connected, shuttle engaged and the signal is given to “take tension” - where slight forward pressure is applied to the shuttle. When in tension, the pilot runs the engines up to full power, AB if needed, and moves the flight controls through their full range, checking instruments and controls. Safety observers from that squadron observe the controls, and check for leaks/problems, they give a thumbs up. When the pilot is satisfied with the control feel, instruments and airplane, they salute the cat officer. Cat officer checks the troubleshooters, forward of the track, and fires the cat.
Airplane goes zero to 170 in two seconds. Awesome.
* The load on the airplane is incredible. The launch bar is about the size of my forearm. In the case of the F-14, the nose strut is compressed (we called it kneeling) for launch and over 200,000 lbs of load goes through that bar into the airframe to accelerate the jet.
It doesn’t always work out. A friend of mine, LCDR Chris “Basher” Blaschum, had the nose strut come apart during a cat shot many years ago. Corrosion internal to the strut weakened its ability to handle that load and it failed. He tried to save the airplane by going into AB and flying it, but there wasn’t enough speed or time. The RIO ejected, and made it. Basher didn’t.
RIP Basher, my friend, until Valhalla.